Epson Laser printer EPL-6100L

I bought the EPL-6100L back in January and at the same time bought an extra ink cartridge. Only now do i need to change to this new cartridge.

After changing to the new cartridge, the output became visibly fainter compared to the previous cartridge.

What could be the problem and how to rectify it?

These are the possible things that i have tried :
– shook the cartridge before putting it in
– reset the toner level
– checked that the photoconductor looks ok
– called the Epson helpdesk & they advised me of the above

Anyone has anymore solutions? Please help!!!!